The causal relationship between the more fast food restaurants and children obesity is usually described as an increased number of fast food restaurants (X) results in more obesity children (Y). It is common to assume that the more fast food restaurants (X), the greater chances that children will become obese (Y). This can be explained by a simple example that most of the children cannot cook by themselves. Therefore, if there are more fast food restaurants near children’s home or school, there will be a larger chance that children will obese because of eating in these restaurants frequently.

However, people would omit one variable which is the influence of parents (Z) in terms of eating habits. In fact, parents are the only one who can decide